- Microplastics can contain chemicals such as polymer additives or environmental contaminants that “stick” to their surface. However, current evidence suggests their contribution to overall chemical exposure is generally insignificant compared with other sources such as food, air, dust, and consumer products.
- The amount of chemical available for release from a microplastic particle is intrinsically limited. Microplastics are tiny particles and additives typically make up a small fraction of the plastic material. This inherently minimizes exposure even before considering whether a chemical could migrate out of a microplastic.
- Laboratory studies sometimes show chemical transfer from microplastics under controlled conditions, but many of these experiments use exposure scenarios that are not representative of real-world environmental or human exposures.
- In its 2019 report, the World Health Organization used modeling approaches that assumed high microplastic intake and high chemical concentrations. Even under these extreme assumptions, the results indicated low health concern for microplastics human exposure.
Microplastics and Chemicals
Microplastics are small particles of plastic that may contain trace amounts of additives such as stabilizers, plasticizers, pigments, or flame retardants. In addition, some chemicals present in the surrounding environment may “stick” (i.e., adsorb) to the surface of the microplastics as well as any other organic particle (e.g., soil). Because of this, microplastics are sometimes described as potential “vectors” that could transport chemicals through the environment or into organisms (GESAMP, 2015).
While this concept is scientifically plausible, its practical significance depends on several factors including the amount of chemical present, the rate at which it can migrate from the plastic, and the relative importance of other exposure pathways. In most cases, these factors suggest that the contribution of microplastics to overall chemical exposure is likely limited (Herzke et al., 2016; Koelmans et al., 2016).
Plastics themselves are generally chemically stable materials designed to retain additives within the polymer matrix. Migration of additives from plastics occurs slowly and is governed by diffusion processes between the additive, the plastics, and the surrounding environment (Leslie et al., 2025). As a result, only a small portion of the chemical present in a particle is typically available for release over short time scales (Koelmans et al., 2016).
Environmental Chemicals on Microplastics
Chemicals present in water or sediments can adsorb onto microplastic surfaces. However, research shows that the amount of chemicals associated with microplastics is often small compared with the concentrations already present in environmental media or biological tissues.
In aquatic environments, organisms are typically exposed to contaminants primarily through food, water, or sediment. Modeling studies and laboratory experiments frequently show that the presence of microplastics does not significantly increase total chemical uptake relative to these dominant exposure pathways. In some cases, microplastics may even act as a temporary sink that reduces the immediate availability of contaminants (Herzke et al., 2016; Ng et al., 2025).
Laboratory Studies and Real-World Relevance
Unlike in the real world, scientists can study the potential effects of particles and chemicals on organisms at concentrations much, much higher than those encountered in the real world (Janzik et al., 2025). Some experimental studies reported increased chemical uptake when organisms are exposed to microplastics containing high concentrations of additives or contaminants (Teuten et sl., 2007). These findings have sometimes been interpreted as evidence that microplastics substantially increase chemical exposure. However, many of these studies rely on test materials that differ significantly from environmental microplastics. Common limitations include the use of unrealistically high particle concentrations, artificially contaminated particles, or poorly characterized materials. While these types of studies can be used to explore possible biological mechanisms at high doses, they can be difficult to draw any conclusions to real world risks. Without standardized test materials and exposure conditions, it can be difficult to determine whether observed effects reflect realistic environmental scenarios (SAPEA, 2019).
Current Scientific Assessments
Recent reviews by international scientific authorities have reached cautious conclusions. The European Food Safety Authority has stated that available data are insufficient to determine exposure levels or health risks associated with microplastics in food. Similarly, the U.S. Food and Drug Administration reports that current evidence does not indicate that microplastics in foods present a risk to human health at this time (FDA, 2024; EFSA, 2025).
Because direct measurements are challenging, modeling approaches are increasingly used to estimate potential exposure. The World Health Organization evaluated chemical exposure from microplastics in drinking water using a highly conservative scenario that assumed high microplastic intake and high chemical concentrations. Even under these extreme assumptions, the results indicated low health concern for microplastics human exposure (WHO, 2019).
The Bottom Line
The hypothesis that microplastics significantly increase chemical exposure remains an active area of research. At present, the available evidence suggests that microplastics are unlikely to be a dominant source of chemical exposure for humans or most organisms. In many cases, existing exposure pathways such as food, drinking water, air, and direct contact with consumer products are likely to be far more important.
Continued research is warranted, particularly studies designed with clear quality assurance, realistic exposure scenarios, and well-characterized test materials. Such work will help determine whether microplastics meaningfully alter chemical exposure under real-world conditions.
Until then, current evidence does not support the conclusion that microplastics represent a major pathway for chemical exposure relative to other sources already present in the environment.
References
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Koelmans, A. A., Bakir, A., Burton, G. A., Janssen, C. R. (2016). Microplastic as a Vector for Chemicals in the Aquatic Environment: Critical Review and Model-Supported Reinterpretation of Empirical Studies. Environ Sci Technol, 50(7), 3315–3326. https://doi.org/10.1021/acs.est.5b06069
Leslie, H. A., Jahnke, A., Rojo-Nieto, E., & Arp, H. P. H. (2025). Plastic-associated chemicals: Late lessons from early equilibrium partitioning science. Environmental Science & Technology. https://doi.org/10.1021/acs.est.5c04383
Ng, D., Chen, Y., Lei, Y. D., Chen, W., Peng, H., Gourlie, S., & Wania, F. (2025). Quantifying the effect of dietary microplastics on the potential for biological uptake of environmental contaminants and polymer additives. Environmental Science & Technology. https://doi.org/10.1021/acs.est.5c02616
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WHO. World Health Organization. (2019). Microplastics in drinking-water. Geneva, Switzerland. ISBN: 978-92-4-151619-8. https://www.who.int/publications/i/item/9789241516198.